We propose to replace a 19-year old electron microscope which is no longer functional with a modern instrument capable of serving the needs of investigators who presently have very limited access to a usable instrument. The new microscope would serve the needs of eight investigators and their associates: six staff members in Zoology at Duke, one in Chemistry at Duke, and one in Zoology at the University of North Carolina at Chapel Hill. The research projects of the participating investigators cover an exceptionally broad range: (1) molcular studies: nucleosome structure; (2) cellular studies: the structural basis of chromosome distribution in mitosis, electron microscopic cytochemistry of enzyme activity regulation, and cellular aspects of calcification; (3) developmental biology: membranes, the cytoskeleton and cell association; lysosomes and cell death during development; (4) biomechanics: ultrastructure of biological materials and the mechanical properties of whole organisms.